Rocks

The ground beneath us is made up of lots of different types of rock.

Every hill, mountain and even under the sea is made entirely of rocks. In some places we can see the rocks, but most of the time the rocks are buried under grass, roads and buildings. When we dig into the ground to make quarries and mines we will always dig through different layers of rock.

What are Rocks made of?

A rock is made of lots of grains which glue together. The grains are made from minerals, which are a type of chemical compound or element that occur naturally. Rocks can be different colours, shapes and sizes but they are always made up of minerals.

Photograph reproduced with the kind permission of the Geevor Archive

The rock cycle: how rocks are formed

There are three main types of rock: igneous, metamorphic and sedimentary.

Granite forms the backbone of Cornwall stretching from Dartmoor in Devon South-westwards to the Isles of Scilly.

Kilas lies just off the coast at Geevor and is far easier to drill than granite, it also takes less explosive to break as it's very brittle. I was stoping on 18 Treglowns in 89-90 and we were just coming out of the granite and into the Kilas. Tin in Kilas equals big money to a stoper as far more ground can be broken per shift and the drills stay sharper longer.